The Equine Disease Communication Center released the following alert from the Oregon Department of Agriculture on Feb. 10:

The Oregon Department of Agriculture has released the quarantine for the wild type EHV-1 positive horse at the Portland Meadows racetrack. The affected horse has made an impressive recovery and now tests negative for EHV-1.

The “wild” strain and the neuropathogenic strains of EHV-1 are different only in one amino acid in their DNA. The two types appear to behave slightly differently in the horse, according to Dr. Josie Traub-Dargatz, professor of equine internal medicine at Colorado State.

“In challenge studies, the amount of virus that's in the blood of the horse seems to be higher with the neuropathogenic strain than the wild type,” she told the Paulick Report in February 2016. “Also, some people believe the scope of disease and the severity among an exposed population would be greater for this neuropathogenic strain, but there have been a couple of outbreaks associated with the wild type and multiple horses were affected.Some laboratories only report that a sample is EHV-1 and don't do subtyping.”

Learn more about testing for EHV-1, disease control, and quarantine procedures here.